1. Field of the Invention
The present invention relates to a tube-plug extracting apparatus capable of automatically extracting a plug from a test tube containing a sample, such as blood.
2. Description of the Related Art
A tube-plug extracting apparatus is described and shown in Paragraph 0007 and FIG. 1 of Jpn. Pat. Appln. KOKAI Publication No. 5-228379. In this apparatus, a plug that is put into a test tube is chucked by a distal end portion of an extracting arm with the tube held by a tube retainer. The extracting apparatus is constructed so that the chucked plug can be automatically extracted from the test tube in the direction in which the plug is pulled off by raising the extracting arm with a cylinder for vertical sliding.
The extracting arm of this apparatus has plug chucking claws on its distal end. Further, the extracting arm has a mechanism that turns the chucked plug through a predetermined angular range around its central axis in conjunction with a tilt guide as the arm is pulled up by the cylinder for vertical sliding.
Test tubes for use as sample containers include test tubes of different bores and lengths (φ13×75 mm, φ13×100 mm, φ16×75 mm, φ16×100 mm, etc.). There are also various types of plugs for these test tubes, including push-in rubber plugs, cork plugs, threaded screw plugs, etc.
However, the tube-plug extracting apparatus described in Jpn. Pat. Appln. KOKAI Publication No. 5-228379 is configured only to extract adaptive standard-typed plugs from test tubes of a fixed size. In other words, it is not provided with any means for adaptation to test tubes of different sizes or plug types. Thus, a lower-limit stop position of the cylinder that vertically moves the extracting arm cannot be adjusted corresponding to a change of length of the test tubes.
In the means for twisting the plug to extract it in conjunction with the tilt guide, an end roller on the extracting arm is configured to be pressed against a slope of the tilt guide by the urging force of a tension spring. This apparatus is designed to reduce the necessary force for plug extraction by turning the plug through only a certain angular range as it is extracted. Thus, the apparatus cannot remove a screw plug that requires several turns for its extraction.